* Wrap the meat in plastic wrap and place in the freezer for 45 minutes.In a large skillet, heat 1 ½ tablespoons of the oil and place over moderately low heat. Add the onion and let cook, stirring occasionally, for 5 minutes. Add the pepper strips, salt and pepper and cook, stirring occasionally, for 10 minutes. The vegetables should be a light golden brown and soft. Remove from the skillet.
* Remove the meat from the freezer and using a very sharp knife very thinly slice the meat. Freezing it slightly will make it easier to slice.
* Heat the remaining tablespoon of oil in the skillet over moderately high heat. Add the beef, salt, and pepper and cook, stirring, for about 4 minutes, or until just cooked through and brown. Push the meat to the side of the skillet and add the cooked vegetables to the other side to warm them up.
* Preheat the oven to 400 degrees. Heat the rolls for 5 minutes or until warm. Slice them open lengthwise and divide the beef and vegetables between the 3 rolls. Divide the cheese slices on top of the hot beef and vegetables and close the sandwich pressing down lightly so the heat of the beef will slightly melt the cheese. Cut the sandwich in half and serve warm.